I am bias and recommend ARUBA, after I searched many locations and have had friends married at the RIU in Cabos and also Cancun I would suggest Cabos or of course Aruba. See below the link to my pictures if you were considering further south (Aruba), I could provide you with the contact details for the packages we had, very reasonable and actually only about $220.00 more per person than Cabos and you are guaranteed great weather!

Goodluck in your search and let me know if you need anything further on Aruba!